No BPV or BOV Important things to know?
Thread Starter
New Member
Joined: 05-05-16
Posts: 4
Likes: 0
From: Estevan SK Canada
No BPV or BOV Important things to know?
Hey guys, i was thinking of blocking off my stock BPV but not put on a BOV. I know alot of people do that for the famous flutter sound, the stututut sound if you know what i mean haha. I know that STIs, EVOs, SILVIAs,etc... run fine without a BOV or BPV and just push the air back through the turbo compressor wheel creating the stututu sound. But ive never heard of a cobalt ss lnf to have that. I just really want to know what you guys think about this. WOuld it do damage, has anybody else tried this or should i just keep my stock bpv and call it a day? Mod list: 22psi zzp tune, corsa catback exhaust, zzp catted downpipe, injen upper charge pipe, aem cold air intake, zzp intercooler. Stock turbo. Thanks guys!!
Compressor surge kills turbos. This will create compressor surge. This will kill your turbo. Please don't do this.
Originally Posted by TurboSmart
2. “Turbo flutter is harmless”
That fluttering noise that some turbocharged cars make when the throttle is suddenly closed, such as during gear changes, is the result of compressor surge. It’s a fairly complex phenomenon which we explain in far more detail here. Basically, that flutter is the sound of a turbocharger trying to push air but failing due to a closed throttle, and it dramatically increases load on the bearings of the turbo. If it occurs at higher engine loads and/or boost levels it can cause premature wear to your turbo. A BOV prevents turbo flutter by venting the air pressure that causes surge.
That fluttering noise that some turbocharged cars make when the throttle is suddenly closed, such as during gear changes, is the result of compressor surge. It’s a fairly complex phenomenon which we explain in far more detail here. Basically, that flutter is the sound of a turbocharger trying to push air but failing due to a closed throttle, and it dramatically increases load on the bearings of the turbo. If it occurs at higher engine loads and/or boost levels it can cause premature wear to your turbo. A BOV prevents turbo flutter by venting the air pressure that causes surge.
Originally Posted by GFB
Which type of blow-off valve makes the fluttering or ‘pigeon' noise?
The short answer is that there is no blow-off valve that makes this noise. Read on to find out why.
Without a BOV, the pressurised air being pumped into the engine by the turbo will have only one path when the throttle is closed: back through the turbo compressor. The fluttering sound is the sound of this air against the blades of the spinning turbo compressor as it tries to flow through it the wrong way.
Car manufacturers fit recirculating (plumb back) BOVs to give the pressurised air an alternate path when the throttle is closed: back into the turbo compressor inlet. This eliminates the ‘undesirable in a brand-new car' fluttering noise.
Aftermarket BOVs typically vent the pressurised air into the atmosphere for the purpose of making noise, and are characterised by the 'standard trumpet' sounds that can be heard here. Some other brands do different things with the air to make different noises, but this is not to be confused with the fluttering noise. Our own ‘whistling trumpet' is one example of this. It can also be heard here.
In some cases, aftermarket BOVs do not flow enough air either as a result of their design, or the way that they are adjusted. In this case, fitting an aftermarket blow-off valve will result in the fluttering noise being emitted from the turbo. While this is extremely popular, it is worth noting that if this is your objective, then simply removing the factory BOV and replacing it with a pair of hose plugs would have been more cost-effective!
Incidentally, fitting a pod air filter can make any fluttering noise that was already present more audible. Also, large front-mounted intercoolers can increase the likelihood of ‘flutter' for any given BOV, due to the larger volume of air present in the intake system. If the BOV is any good, some adjustment of the spring preload would be all that is necessary to once again eliminate the flutter.
Finally, it is possible to set up your GFB blow-off valve to cause some ‘pigeon' noise by increasing the spring preload slightly (turning the spring preload adjustment clockwise). The aim is to have the flutter occur at low rpm and boost, while allowing the BOV to vent freely at higher rpm and boost levels. Experiment with it; you can't do any harm!
The short answer is that there is no blow-off valve that makes this noise. Read on to find out why.
Without a BOV, the pressurised air being pumped into the engine by the turbo will have only one path when the throttle is closed: back through the turbo compressor. The fluttering sound is the sound of this air against the blades of the spinning turbo compressor as it tries to flow through it the wrong way.
Car manufacturers fit recirculating (plumb back) BOVs to give the pressurised air an alternate path when the throttle is closed: back into the turbo compressor inlet. This eliminates the ‘undesirable in a brand-new car' fluttering noise.
Aftermarket BOVs typically vent the pressurised air into the atmosphere for the purpose of making noise, and are characterised by the 'standard trumpet' sounds that can be heard here. Some other brands do different things with the air to make different noises, but this is not to be confused with the fluttering noise. Our own ‘whistling trumpet' is one example of this. It can also be heard here.
In some cases, aftermarket BOVs do not flow enough air either as a result of their design, or the way that they are adjusted. In this case, fitting an aftermarket blow-off valve will result in the fluttering noise being emitted from the turbo. While this is extremely popular, it is worth noting that if this is your objective, then simply removing the factory BOV and replacing it with a pair of hose plugs would have been more cost-effective!
Incidentally, fitting a pod air filter can make any fluttering noise that was already present more audible. Also, large front-mounted intercoolers can increase the likelihood of ‘flutter' for any given BOV, due to the larger volume of air present in the intake system. If the BOV is any good, some adjustment of the spring preload would be all that is necessary to once again eliminate the flutter.
Finally, it is possible to set up your GFB blow-off valve to cause some ‘pigeon' noise by increasing the spring preload slightly (turning the spring preload adjustment clockwise). The aim is to have the flutter occur at low rpm and boost, while allowing the BOV to vent freely at higher rpm and boost levels. Experiment with it; you can't do any harm!
Last edited by YelloEye; Jun 15, 2016 at 02:56 AM.
First of all, Compressor surge is defined as a turbo that pushes more compressed air than the Head can flow. This causes a backlash or "surge" of compressed air pushing back on the turbo CHRA and can kill turbos
Turbo "flutter" or the noise that people like, is due to the throttle body being closed and compressed air being pushed back into the turbo which chops the air. this is almost the same as compressor surge, except that the load is different.
with that being said, I had flutter on my k04 turbo for years and had no issues. This is just my personal experience. I had turbo flutter on the ZFR too. if you want a sweet sounding bov, get the Forge VTA BOV and use the yellow spring. I had flutter at normal driving but when I went WOT it vented like normal.
Compressor surge is bad. Turbo flutter, is not. Stock BPVs flutter sometimes because even the best bpv systems cannot dump the compressed air fast enough.
Turbo "flutter" or the noise that people like, is due to the throttle body being closed and compressed air being pushed back into the turbo which chops the air. this is almost the same as compressor surge, except that the load is different.
with that being said, I had flutter on my k04 turbo for years and had no issues. This is just my personal experience. I had turbo flutter on the ZFR too. if you want a sweet sounding bov, get the Forge VTA BOV and use the yellow spring. I had flutter at normal driving but when I went WOT it vented like normal.
Compressor surge is bad. Turbo flutter, is not. Stock BPVs flutter sometimes because even the best bpv systems cannot dump the compressed air fast enough.
New Member
Joined: 02-11-16
Posts: 95
Likes: 4
From: NJ
First of all, Compressor surge is defined as a turbo that pushes more compressed air than the Head can flow. This causes a backlash or "surge" of compressed air pushing back on the turbo CHRA and can kill turbos
Turbo "flutter" or the noise that people like, is due to the throttle body being closed and compressed air being pushed back into the turbo which chops the air. this is almost the same as compressor surge, except that the load is different.
with that being said, I had flutter on my k04 turbo for years and had no issues. This is just my personal experience. I had turbo flutter on the ZFR too. if you want a sweet sounding bov, get the Forge VTA BOV and use the yellow spring. I had flutter at normal driving but when I went WOT it vented like normal.
Compressor surge is bad. Turbo flutter, is not. Stock BPVs flutter sometimes because even the best bpv systems cannot dump the compressed air fast enough.
Turbo "flutter" or the noise that people like, is due to the throttle body being closed and compressed air being pushed back into the turbo which chops the air. this is almost the same as compressor surge, except that the load is different.
with that being said, I had flutter on my k04 turbo for years and had no issues. This is just my personal experience. I had turbo flutter on the ZFR too. if you want a sweet sounding bov, get the Forge VTA BOV and use the yellow spring. I had flutter at normal driving but when I went WOT it vented like normal.
Compressor surge is bad. Turbo flutter, is not. Stock BPVs flutter sometimes because even the best bpv systems cannot dump the compressed air fast enough.
WOT surge KILLS the thrust bearing in a turbo in a hurry. Avoid it at all cost.
But running without a BPV or BOV does not cause or affect WOT surge. It only creates off throttle flutter. I researched this heavily years ago in another platform and came to the conclusion that it was perfectly fine to run without a BPV or BOV on my Toyota 3sgte platform. I did so for 5 years/50K miles of driving and the turbo was just fine at the end of that. I also experienced must faster boost build up after a shift, almost without loss of boost, even though I let off the throttle between shifts.
I am not sure on the LNF if the PCM uses control of this to help reduce boost under certain conditions though. So there might be a consideration to that if it does use the BPV as a safety relief valve in some way.
Otherwise I do not think there is any harm in it, and probably get better boost response after shifts (assuming you are not using NLS, because I think NLS leaves the BPV closed anyway).
Compressor surge isn't defined as a head that doesn't flow well enough for its paired turbo, though that can cause compressor surge.
Having a BPV/BOV spring that is too heavy will have flutter, which can be harmless, but could also cause compressor surge by allowing that excess air pressure wave to impact the turbo fins when the throttle is suddenly slammed shut.
Yes the load is different, and it's not WOT full load compressor surge. But I can't imagine one that doesn't flutter won't negate the possibility of compressor surge better.
All that aside, what the OP was originally asking would not be good for the life of the turbo regardless of what it's called.
Originally Posted by TurboByGarrett
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are:
-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
-The outlet plumbing for the bypass valve is too small or restrictive
-The turbo is too big for the application
-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
-The outlet plumbing for the bypass valve is too small or restrictive
-The turbo is too big for the application
Yes the load is different, and it's not WOT full load compressor surge. But I can't imagine one that doesn't flutter won't negate the possibility of compressor surge better.
All that aside, what the OP was originally asking would not be good for the life of the turbo regardless of what it's called.
Senior Member
Joined: 06-10-12
Posts: 2,880
Likes: 63
From: Manitoba, Canada
First of all, Compressor surge is defined as a turbo that pushes more compressed air than the Head can flow. This causes a backlash or "surge" of compressed air pushing back on the turbo CHRA and can kill turbos
Turbo "flutter" or the noise that people like, is due to the throttle body being closed and compressed air being pushed back into the turbo which chops the air. this is almost the same as compressor surge, except that the load is different.
with that being said, I had flutter on my k04 turbo for years and had no issues. This is just my personal experience. I had turbo flutter on the ZFR too. if you want a sweet sounding bov, get the Forge VTA BOV and use the yellow spring. I had flutter at normal driving but when I went WOT it vented like normal.
Compressor surge is bad. Turbo flutter, is not. Stock BPVs flutter sometimes because even the best bpv systems cannot dump the compressed air fast enough.
Turbo "flutter" or the noise that people like, is due to the throttle body being closed and compressed air being pushed back into the turbo which chops the air. this is almost the same as compressor surge, except that the load is different.
with that being said, I had flutter on my k04 turbo for years and had no issues. This is just my personal experience. I had turbo flutter on the ZFR too. if you want a sweet sounding bov, get the Forge VTA BOV and use the yellow spring. I had flutter at normal driving but when I went WOT it vented like normal.
Compressor surge is bad. Turbo flutter, is not. Stock BPVs flutter sometimes because even the best bpv systems cannot dump the compressed air fast enough.
What kind of noise did you get? Mine was a constant pulse sound.
New Member
Joined: 02-11-16
Posts: 95
Likes: 4
From: NJ
Compressor surge isn't defined as a head that doesn't flow well enough for its paired turbo, though that can cause compressor surge.
Having a BPV/BOV spring that is too heavy will have flutter, which can be harmless, but could also cause compressor surge by allowing that excess air pressure wave to impact the turbo fins when the throttle is suddenly slammed shut.
Yes the load is different, and it's not WOT full load compressor surge. But I can't imagine one that doesn't flutter won't negate the possibility of compressor surge better.
All that aside, what the OP was originally asking would not be good for the life of the turbo regardless of what it's called.
Having a BPV/BOV spring that is too heavy will have flutter, which can be harmless, but could also cause compressor surge by allowing that excess air pressure wave to impact the turbo fins when the throttle is suddenly slammed shut.
Yes the load is different, and it's not WOT full load compressor surge. But I can't imagine one that doesn't flutter won't negate the possibility of compressor surge better.
All that aside, what the OP was originally asking would not be good for the life of the turbo regardless of what it's called.
Each person will have to make up their own mind I guess and do what they think is best.
For the poster who states he hears a pulsing at WOT, that sounds like true dangerous compressor surge and I would be very careful about it.
That turbo flutter when u don't have a bpv or bov is not the noise people like, it's very annoying. The noise people like is a bov that opens and closes super fast causing a similar less annoying noise. The forge bpv does this on the zfr at high boost . Love it
No its not. Flutter is when the compressed air gets chopped by the blades...which is what everyone likes.
Your definition makes no sense at all. Do you understand how a BPV/BOV works?
No, if you have flutter at full boost...that is very bad. I had surge at full boost on the ZFR because it spooled so damn fast for the LNF that Term had to back it out a bit.
Senior Member
Joined: 06-10-12
Posts: 2,880
Likes: 63
From: Manitoba, Canada
ok let me say it again. there is one when the bpv opens and some air still hits the turbo fins and u get a nice flutter sound, then there is the one with no bov, which sound crappy. in our cars anyway. its awful
Why is everyone arguing over a mod to make a noise???? Why not just have a normal functioning car? Let your car be unique in its own ways, don't make it like other people's cars, and you can still hear the turbo I can assure you that.
New Member
Joined: 02-11-16
Posts: 95
Likes: 4
From: NJ
Yes, I agree that I would never do it for just noise. But if one wanted to do this there is a performance benefit, as it keeps the intake tract charged better between shifts (since the BPV dumps the pressure when it is working) for a faster response after shifts (assuming you are not using NLS).
Hey guys, i was thinking of blocking off my stock BPV but not put on a BOV. I know alot of people do that for the famous flutter sound, the stututut sound if you know what i mean haha. I know that STIs, EVOs, SILVIAs,etc... run fine without a BOV or BPV and just push the air back through the turbo compressor wheel creating the stututu sound. But ive never heard of a cobalt ss lnf to have that. I just really want to know what you guys think about this. WOuld it do damage, has anybody else tried this or should i just keep my stock bpv and call it a day? Mod list: 22psi zzp tune, corsa catback exhaust, zzp catted downpipe, injen upper charge pipe, aem cold air intake, zzp intercooler. Stock turbo. Thanks guys!!
Thread
Thread Starter
Forum
Replies
Last Post
califcarm
08-10 SS Turbocharged General Discussion
10
Mar 4, 2016 09:44 PM
SSMiKE8
Parts
3
Feb 25, 2016 06:07 PM